KR20040054614A - Liquid crystal display and its driving method - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof, wherein the frequency converter 101 provided in the liquid crystal display device simultaneously writes the pixels on L gate lines of the liquid crystal panel between the image signals constituting the input video signal. Non-image signals are inserted at intervals of one line to the image signals of L (L is an integer of 2 or more) lines to generate an output image signal, and the number of horizontal scanning periods forming one frame period is (L + 1) Adjust the number of horizontal scanning periods included in the vertical blanking periods in the output video signal to be × (2N + 1) (N is an integer), thereby inverting anti-transition drive using the OCB mode liquid crystal panel. In this case, the increase of the driving frequency is suppressed, and the luminance unevenness caused by the AC drive of the liquid crystal panel is prevented and the cost is reduced.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY AND ITS DRIVING METHOD}

BACKGROUND ART Liquid crystal displays have been used a lot as display devices such as computer devices, but thereafter, their use in TV applications is also expected to increase. However, TN (Twisted Nematic) mode liquid crystal panels, which are widely used at present, have shortcomings with a narrow viewing angle and insufficient response speed. Therefore, there is a big problem to be solved in using the TN mode liquid crystal panel for TV use, such as the reduction of contrast due to parallax or the blurred outline in moving image display.

Recently, research on the OCB mode has been conducted in place of the TN mode. Since the OCB mode has a wider viewing angle and a higher response speed than the TN mode, the OCB mode is suitable for moving picture display.

26 shows the configuration of a general liquid crystal panel. This is common in both TN mode and OCB mode. In Fig. 26, X1 to Xn are gate lines, Y1 to Yn are source lines, and thin-film transistors (hereinafter referred to as TFTs) as switching elements are provided at each intersection of the gate lines X1 to Xn and the source lines Y1 to Yn ( 2604 is provided, and the drain electrode of each TFT 2604 is connected to the pixel electrode of each pixel 2605 of the liquid crystal panel, respectively. In each pixel 2605, a liquid crystal is sandwiched between the pixel electrode and the counter electrode. The potential of the counter electrode is controlled by the counter driver 2603.

&Quot; 2602 " is a gate driver that supplies gate pulses for controlling on / off of the state of the TFT 2604 to the gate lines X1 to Xn. The gate driver 2602 sequentially applies a potential for turning on the state of the TFT 2604 to the gate lines X1 to Xn in synchronization with the supply of data to the source lines Y1 to Yn. &Quot; 2601 " is a source driver which controls the potential of the pixel electrode. The difference between the potential of the pixel electrode controlled by the source driver 2601 and the potential of the counter electrode controlled by the counter driver 2603 becomes a voltage related to the liquid crystal, and the transmittance of each pixel 2605 is determined by the voltage. do.

By the way, in the case of using the liquid crystal panel of the OCB mode, a unique procedure that is not present in the TN mode is required in the first step of starting image display. The OCB cell can handle two states: bend orientation and splay orientation. In order to display an image in the OCB mode liquid crystal panel, the OCB cell needs to be in a bend alignment state. However, since an OCB cell is normally in a splay orientation, it is necessary to change the state of the OCB cell from splay orientation to bend orientation when displaying an image. Hereinafter, the state change from such a splay orientation to a bend orientation is called "transition". In order to transfer the OCB cell, a unique procedure such as applying a high voltage for a predetermined time is required, but this order is omitted because it does not directly relate to the present invention.

When the OCB cell transitions through a unique sequence described above and enters a bend alignment state, an image can be displayed. However, if the state in which no voltage is applied to the OCB cell more than a predetermined level continues for a predetermined time or more, the state of the OCB cell returns from the bend orientation to the spray orientation. Hereinafter, the state change from such bend orientation to spray orientation is called "reverse transition." Therefore, in order to display an image continuously using the liquid crystal panel of OCB mode, it is necessary to prevent reverse transition. To prevent the reverse transition, as disclosed in Japanese Patent Application Laid-Open No. 11-109921 or April 25, 1999 (Vo1.3.No.2), P99 (17) to P106 (24), OCB It is good to apply high voltage to the cell regularly. Hereinafter, the driving method of the liquid crystal panel which periodically applies a high voltage to the OCB cell is called " reverse shift prevention driving ".

However, in a general liquid crystal panel represented by OCB mode or TN mode, it is well known that irrationality such as burn-in occurs when a DC voltage is applied to the liquid crystal cell. Therefore, when driving the liquid crystal panel, it is necessary to perform so-called alternating current driving, which alternately reverses the polarity of the voltage applied to the liquid crystal cell. This corresponds to the case where the liquid crystal panel is driven by the inversion preventing drive described above. However, Japanese Patent Application Laid-Open No. 11-109921 or the Japanese Liquid Crystal Journal do not describe the structure and operation of the liquid crystal display device when the AC drive is applied to the anti-reverse drive. It is not clear from the above document how to apply alternating current drive to.

However, in the above document, in order to alternately write an image signal and a high low voltage signal (a signal for periodically applying a high voltage to an OCB cell), a method of disposing a source driver in both up and down, and a method of doubling the driving frequency is provided. Is disclosed. However, these methods have the problem of increasing the cost because two source drivers are required, and the problem that the writing time of the signal is reduced and the writing of the signal to the OCB cell becomes insufficient because the driving frequency is doubled. Thus, the inventors of the present invention have realized a reverse transition prevention drive that suppresses an increase in the driving frequency. Hereinafter, as a related art of the present invention, a liquid crystal display device to which the reverse transition prevention driving is applied will be described.

27 shows the configuration of the liquid crystal display device related to the related art. In FIG. 27, "2701" denotes a frequency converter which performs frequency conversion on an input video signal, "2702" denotes a drive pulse generator that generates pulses for controlling the source driver and the gate driver, respectively, and "2601" denotes a source drive. The parent, "2602", represents the gate driver, and the "2703" represents the liquid crystal panel of the OCB mode. For convenience, the gate line of the liquid crystal panel 2703 is set to 12 lines, and one frame period is composed of 12 horizontal scanning periods.

In this liquid crystal display, for each pixel on the liquid crystal panel 2703, an image signal constituting an input video signal and a non-image signal irrelevant to the input video signal are recorded once in one frame period. Here, the non-image signal is a signal for applying a high voltage to the OCB cell for preventing reverse transition. In order to realize such a recording, it is necessary to appropriately insert a non-picture signal between the image signals constituting the input video signal. Therefore, the frequency converter 2701 of the present liquid crystal display inserts one non-image signal for each of the four image signals (the image signal for four lines) of the input image signal to generate an output image signal, and this is the source driver 2601. To be sent). However, simply inserting the non-picture signal changes the length of one frame period, so that the frequency converter 2701 also performs frequency conversion at the same time. That is, in order to transmit the five signals consisting of four image signals and one non-image signal to the source driver at the time when four image signals are input as input image signals (i.e., four horizontal scanning periods), 1.25 Double frequency conversion takes place.

28 illustrates a specific configuration of the frequency converter 2701. The control signal generator 2801 generates a write clock, a read clock, a readable signal, an output switching control signal, and an output synchronous signal based on the input synchronous signal, respectively. The input video signal is recorded in the line memory 2802 in synchronization with the recording clock. The input video signal recorded in the line memory 2802 is read out from the line memory 2802 in synchronization with a read clock having a frequency of 1.25 times the recording clock. The output signal selector 2804 selects one of the output of the line memory 2802 and the output of the non-image signal generator 2803 based on the output switching control signal and outputs it as an output video signal. 29 shows signal waveforms related to the above processing.

30 illustrates the input / output characteristics of the source driver 2601. An output video signal output from the frequency converter 2701 is input to the source driver 2601, and the signal level of the output video signal is larger than the reference potential according to the polarity control signal output from the drive pulse generator 2702. The outputs are alternately switched to level or small level. If the output signal level of the source driver 2601 is greater than the reference potential, a positive voltage is applied to the liquid crystal cell. On the contrary, if the output signal level of the source driver 2601 is less than the reference potential, a negative voltage is applied to the liquid crystal cell. Is approved. Further, as the signal level of the output video signal is larger, the output signal level of the source driver 2601 approaches the reference potential (that is, the voltage applied to the liquid crystal cell is smaller).

In Fig. 31, the gate pulses P1 to P12 select the gate lines GL1 to GL12 on the liquid crystal panel 2703 respectively during the HI period. In addition, "+" and "-" shown in the HI period of each gate pulse P1 to P12 represent the polarity (that is, the polarity of the applied voltage) of the signal written to the pixel on the gate line selected by the gate pulse. . In the period T0_0, the gate pulses P5 to P8 become HI at the same time, and non-image signals are simultaneously recorded bipolarly in the image on the gate lines GL5 to GL8. In the subsequent periods T0_1 to T0_4, the gate pulses P1 to P4 become HI in order, and the image signals S1 to S4 are sequentially inputted bipolarly to the pixels on the gate lines GL1 to GL4. In the period T0_5, the gate pulses P9 to P12 become HI at the same time, and non-image signals are simultaneously written negatively to the gate lines GL9 to GL12. In the subsequent periods T0_6 to T0_9, the gate pulses P5 to P8 become HI in order, and the image signals S5 to S8 are written in the negative order to the pixels on the gate lines GL5 to GL8, respectively. Here, each pixel on the gate lines GL5 to GL8 has a period from when the non-image signal is written until the image signal is written thereafter, that is, T0_1 to T0_5, T0_1 to T0_6, T0_1 to T0_7, and T0_1 to T0_8, respectively. In this period, the non-image signal is maintained. In this way, all the gate lines on the liquid crystal panel 107 are selected twice in one frame period, and image signals and non-image signals are written once in the pixel on each gate line in one frame period.

In the period T1_0 of the next frame period, the gate pulses P5 to P8 become HI at the same time, and the non-image signal is written to the pixels on the gate lines GL5 to GL8 as negative (polarity opposite to the previous frame). do. In the subsequent periods T1_1 to T1_4, the gate pulses P1 to P4 become HI in turn, and the image signals S'1 to S'4 are negative for the pixels on the gate lines GL1 to GL4, respectively. In reverse polarity).

As described above, according to the liquid crystal display shown in Fig. 27, it is possible to alternately record an image signal and a non-image signal for each pixel on the liquid crystal panel 2703 while suppressing an increase in driving frequency (Japanese Patent Application No. 2001-131414). .

However, when performing reverse transition prevention driving (i.e., reverse transition prevention driving in which an increase in driving frequency is suppressed by simultaneously writing non-image signals to a plurality of gate line pixels at the same time as in the liquid crystal display device), one frame period is constituted. There is a limit to the number of horizontal scanning periods.

For example, in the method of simultaneously recording non-image signals on four gate lines as in the liquid crystal display device, the number of horizontal scanning periods constituting one frame period at the time after frequency conversion (that is, in the output video signal) is five bases. Need to be doubled. In the example of Fig. 31, this condition is satisfied because the number of horizontal scanning periods (periods T0_0 to T0_14) constituting one frame period in the output video signal is 15 (base multiple of 5). In general, this restriction requires that the number of horizontal scanning periods constituting one frame period at the time after the frequency conversion is (L + 1) × (2N + 1) in the method of simultaneously recording non-image signals on L gate lines. There is. If this restriction is not satisfied, luminance unevenness occurs such that the display screen of the liquid crystal panel 2703 becomes relatively bright in certain lines and relatively dark in certain lines. The cause will be briefly described below.

32 shows various signal waveforms in the method of simultaneously writing non-image signals to three gate lines. In this example, since the number of horizontal scanning periods constituting one frame period in the output video signal is 16 and not an odd multiple of 4 (= 3 + 1), the above condition is not satisfied. In Fig. 32, when attention is paid to the change in the polarity of the signal recorded in the pixel on each gate line, the image signals of the polarity opposite to the non-image signal are necessarily immediately before the non-image signal is recorded for the gate lines GL1 to GL3. Is recorded. On the other hand, for the gate lines GL4 to GL12, an image signal having the same polarity as that of the non-image signal is always recorded immediately before the non-image signal is recorded. However, when a signal having a polarity opposite to that of the signal is recorded for a liquid crystal cell in which all signals of a certain polarity are recorded, there is a problem that the recording of the signal becomes insufficient compared to the case of recording a signal having the same polarity as the signal. have. Therefore, in the example of FIG. 32, the recording of the non-image signal for the pixels on the gate lines GL1 to GL3 is insufficient compared with the recording of the non-image signal for the pixels on the other gate lines GL4 to GL12. As a result, luminance is emitted in the portion corresponding to the gate lines GL1 to GL3 on the liquid crystal panel 107 and the portion corresponding to the gate lines GL4 to GL12. If the above constraint is not satisfied, luminance unevenness occurs.

In order to prevent such luminance unevenness, it is necessary to adjust the number of horizontal scanning times of the video signal. However, if the number of horizontal scanning times is simply increased or decreased, recording of the image signals to the line memory 2802 as shown in FIG. There is a possibility that the timing of reading and the reading is shifted, and proper transmission of the image signal is impossible (that is, the image signal is lost) only by the line memory 2802 for one line. In order to reliably avoid such irregularities, it is necessary to provide a memory capable of simultaneously storing more than one line of image signals, such as a frame memory, resulting in an increase in the cost of the liquid crystal display device.

Therefore, it is an object of the present invention to provide a liquid crystal display device which is capable of preventing reverse inversion driving with an increase in driving frequency, suppressing occurrence of luminance nonuniformity, displaying a good image, and having a low cost.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device suitable for displaying a moving image using a liquid crystal panel or using a liquid crystal panel in an OCB (Optically Self-Compensated Birefringence) mode.

1 is a block diagram showing the configuration of a liquid crystal display device according to a first embodiment of the present invention;

2 is a block diagram showing a configuration of a frequency converter;

3 is a view showing the operation of the frequency converter in the effective region period;

4 is a view showing the operation of the frequency converter in the vertical blanking period;

5 is a view showing the operation of the frequency converter in the vertical blanking period;

6 is a diagram showing the relationship between the horizontal scanning period before and after frequency conversion;

7 illustrates an output of a source driver and a gate driver;

8 is a diagram showing a relationship between a horizontal scan period before and after frequency conversion;

9 is a block diagram showing the configuration of a liquid crystal display device according to a second embodiment of the present invention;

10 is a view for explaining the principle of the second embodiment;

11 is a diagram showing the relationship between the horizontal scanning period before and after frequency conversion;

12 is a block diagram showing the configuration of an Hr calculation unit;

Fig. 13 is a diagram showing the relationship between the horizontal scanning period before and after frequency conversion;

14 is a block diagram showing the configuration of a liquid crystal display device according to a third embodiment of the present invention;

15 is a block diagram showing a configuration of a modification of the third embodiment;

Fig. 16 is a diagram showing the relationship between the horizontal scanning period before and after frequency conversion;

17 is a view for explaining the cause of the luminance non-uniformity,

18 is a view showing a state of luminance unevenness,

19 is a block diagram showing the configuration of a liquid crystal display device according to a fourth embodiment of the present invention;

20 is a diagram showing a relationship between a horizontal scan period before and after frequency conversion;

21 shows each horizontal scanning period in the vertical blanking period,

22 is a diagram showing a state of luminance unevenness;

Fig. 23 is a block diagram showing the structure of a liquid crystal display device according to a fifth embodiment of the present invention;

24 is a block diagram showing a configuration of a frequency converter;

25 is a diagram showing the relationship between the horizontal scanning period before and after frequency conversion;

26 is a view showing the configuration of a general liquid crystal panel;

27 is a block diagram showing the construction of a liquid crystal display device related to the related art;

28 is a block diagram showing a configuration of a frequency converter;

29 is a view showing the operation of the frequency converter;

30 is a diagram showing a relationship between a polarity control signal and an output of a source driver;

31 shows an output of a source driver and a gate driver, and

32 is a diagram showing outputs of a source driver and a gate driver.

In order to achieve the above object, the present invention employs the following configurations. In addition, the reference numerals in the parentheses have shown a correspondence with the embodiments described later for better understanding of the present invention, and do not limit the scope of the present invention.

The liquid crystal display device of the present invention displays an image by driving a liquid crystal panel based on an input video signal. The liquid crystal display device includes a liquid crystal panel 107 having a plurality of source lines and a plurality of gate lines, and an image signal constituting the input video signal. The non-image signal, which is simultaneously recorded in the pixels on the L gate lines of the liquid crystal panel, is inserted at intervals of one line with respect to the image signal of the L lines to generate an output image signal, and further comprises a horizontal frame forming one frame period. A frequency converter 101 for adjusting the number of horizontal scanning periods of the output video signal such that the number of syringes is (L + 1) × (2N + 1) (N is an integer), and the output image generated by the frequency converter A driver 105 for driving the liquid crystal panel based on the signal, and the frequency converter adjusts the number of horizontal scanning periods constituting one frame period by increasing or decreasing the number of horizontal scanning periods included in the vertical blanking period. It is characterized by. Thereby, luminance nonuniformity does not generate | occur | produce even when a non-image signal is inserted regularly and an AC drive of a liquid crystal panel is carried out. Further, since the adjustment of the number of horizontal scanning periods is performed in the vertical blanking period, a memory for simultaneously storing more than one line of image signals is unnecessary. In addition, the number of horizontal scanning periods can be adjusted without affecting the image displayed on the liquid crystal panel. In addition, the term "one frame period" means a period including not only an effective video period but also a vertical blanking period following it. In addition, "the number of horizontal scanning periods constituting one frame period" is, in other words, the number of chopped periods by the horizontal synchronization signal in one frame period, and specifically, the input image of FIG. 50 for the signal and 65 for the output video signal.

In addition, in the claims, the term "reverse transition" means a phenomenon in which the state of the OCB cell is shifted from the bend orientation to the splay orientation. The term "adjustment period included in the vertical blanking period" does not exclude the case where the vertical blanking period and the adjustment period coincide.

Hereinafter, various embodiments of the present invention will be described with reference to the drawings.

(1st embodiment)

1 shows a configuration of a liquid crystal display device according to a first embodiment of the present invention. In FIG. 1, a liquid crystal display device includes a frequency converter 101, a drive pulse generator 102, and a period discriminator ( 103, a selector 104, a source driver 105, a gate driver 106, and a liquid crystal panel 107. Here, the liquid crystal panel 107 is set to the OCB mode.

In the liquid crystal display device, an input video signal and a corresponding input synchronous signal (including a horizontal synchronous signal and a vertical synchronous signal) are supplied. The period discrimination unit 103 determines the vertical blanking period based on the input synchronization signal. The selector 104 selects different frequency division clocks (division clock number A, frequency division clock number B) in the vertical blanking period and other periods based on the determination result by the period determination unit 103, and then the frequency converter 101 Supplies). The frequency converter 101 performs a frequency conversion process on the input video signal and the input synchronous signal, and also performs a non-picture signal at predetermined intervals at intervals between the image signals (video signals for one line) constituting the input video signal. (Signal for applying high voltage to OCB cell to prevent reverse transition) is inserted. In this embodiment, the frequency converter 101 converts the frequency by 1.25 times and inserts one non-image signal for each of the four image signals to generate an output video signal.

2 shows the configuration of the frequency converter 101. The line memory 202 temporarily stores one line of image signals. The control signal generator 201 generates various control signals based on the input synchronous signal and the number of divided clocks selected by the selector 104. Specifically, the control signal generation unit 201 stores a write clock (WRITE CLK) for controlling the timing of recording each image signal of the input image signal in the line memory 202 or an image signal stored in the line memory 202. For controlling the selection operation of the read signal READ ENA or the output signal selector 204 which enables reading of data from the line memory 202 and the read clock READ CLK for controlling the timing of reading. An output synchronizing signal which is a synchronizing signal corresponding to an output switching control signal or a frequency-converted video signal (output video signal) is generated. The non-picture signal generator 203 outputs a non-picture signal. The output signal selector 204 alternately selects the output of the line memory 202 and the output of the non-image signal generator 203 based on the output change control signal from the control signal generator 201, and outputs the output video signal. Output as. Write processing and reading processing for the line memory 202 are the same as those shown in FIG.

Hereinafter, for convenience of explanation, the number of horizontal scanning periods constituting one frame period in the input image signal is 50 (of which the number of horizontal scanning periods in the effective image period is 40 and the horizontal scanning period in the vertical blanking period For example, the operation of the liquid crystal display device will be described. In addition, one frame period is set to 20 ms.

In this case, when frequency conversion of 1.25 times is simply performed on the input video signal, the number of horizontal scanning periods constituting one frame period in the output video signal is 50 × 1.25 = 62.5, and (L + 1) No arrangement is made (also L = 4 in this embodiment). Thus, luminance unevenness occurs. Thus, the frequency converter 101 changes the number of horizontal scanning periods in the effective video period from 40 to 50 and changes the number of horizontal scanning periods in the vertical blanking period from 10 to 15 in the effective video period. As a result, the number of horizontal scanning periods constituting one frame period in the output video signal is 50 + 15 = 65, which is an odd multiple of (L + 1).

In order to realize the above operation of the frequency converter 101, the number of divided blocks is switched between the effective video period and the vertical blanking period.

For example, when the number of horizontal dot clocks of the input video signal is 100, the frequency of the recording clock of the line memory 202 is 100 x 50 / 0.02 = 250 Hz. The frequency converter 101 performs frequency conversion of 1.25 times, and the frequency of the read clock of the line memory 202 is 250 x 1.25 = 312.5 kHz.

Since the effective video period is 20 × 40/50 = 16ms, and the number of horizontal scanning periods included in the effective video period in the output video signal is 50, the number of divided clocks in the effective video period is 312.5 × 16/50 = 100. good.

On the other hand, since the vertical blanking period is 20 × 10/50 = 4ms and the number of horizontal scan periods included in the vertical blanking period in the output video signal is 15, the number of divided clocks in the vertical blanking period is 312.5 × 4/15 = 83. It is good to set it as (cut below decimal point). Although the cutting is performed below the decimal point for the convenience of explanation, the division may be performed while maintaining the precision of the decimal point (the method is already known, so the description is omitted here).

That is, the divided clock number A shown in FIG. 1 may be set to 100, and the divided clock number B to 83 may be set in advance. The selector 104 selects the divided clock number A 100 for the effective video period, and selects the divided clock number B 83 for the vertical blanking period. The control signal generator 201 of the frequency converter 101 generates and outputs an output synchronization signal and an output video signal based on the number of divided clocks supplied from the selector 104. 3 and 4 show signal waveforms showing the same operation as that of the frequency converter 101. In particular, FIG. 3 shows the operation in the effective video period, and FIG. 4 shows the operation in the vertical blanking period. In addition, although the output signal selector 204 always selects the output of the non-image signal generator 203 in FIG. 4, as shown in FIG. 5, the output of the line memory 202 and the non-image signal generator are illustrated. The output of 203 may be selected alternately. This is because in the present embodiment, portions other than the non-image signals in the output video signal shown in Fig. 4 are not recorded in the pixels of the liquid crystal panel 107, and this does not affect the display.

6 shows the relationship between the horizontal scanning period before and after the frequency conversion. For the effective picture period, the number of horizontal scan periods is changed from 40 to 50. On the other hand, for the vertical blanking period, the number of horizontal scanning periods is changed from 10 to 15. As a result, the number of horizontal scanning periods constituting one frame period in the output video signal is 65, which is an odd multiple of 5 (the number of lines 4 for simultaneously recording non-image signals plus 1). The output video signal generated in this way is supplied to the source driver 105, and is written to the pixel on the predetermined gate line based on the gate pulse output from the gate driver 106. FIG. 7 shows the output signal of the sword driver 105 and the output signal (gate pulse) of the gate driver 106 from the effective video period of one frame to the vertical blanking to the next valid video period. In the example of FIG. 7, before the image signal is recorded in each pixel (before the 16-19 horizontal scanning period), the non-image signal is recorded, and the non-image signal is recorded in the 16-19 horizontal scanning period (that is, on average of one frame period). Approximately 27%).

As another embodiment of Fig. 8, the number of horizontal scanning periods constituting one frame period in the input image signal is 56 (the number of horizontal scanning periods in the effective video period is 45, and the number of horizontal scanning periods in the vertical blanking period is 11 ), Frequency conversion of 1.2 times to insert one non-image signal for every five image signals to generate an output video signal (i.e., to simultaneously record non-image signals to pixels on five gate lines). The relationship between the horizontal scanning period before and after the conversion is shown. In this case, in order to prevent the occurrence of luminance unevenness, the number of horizontal scanning periods constituting one frame period in the output video signal needs to be an odd multiple of six. In the example of Fig. 8, the number of horizontal scanning periods in the effective image period is changed from 45 to 54, and the number of horizontal scanning periods in the vertical blanking period is changed from 11 to 12 to determine the horizontal scanning time that constitutes one frame period. The number is 66 (base number of 6). In this case, the divided clock number A shown in FIG. 1 is set to 100 and the divided clock number B is set to 110, and the selector 104 sets the divided clock number A 100 in the effective video period, and in the vertical blanking period. The divided clock number B 110 may be selected.

As described above, according to the first embodiment, the frequency converter 101 outputs a non-image signal simultaneously written to pixels on L gate lines of the liquid crystal panel 107 between image signals constituting the input video signal. The output video signal is generated by inserting the image signal for each line at intervals of one line, and the number of horizontal scanning periods forming one frame period is (L + 1) × (2N + 1) (N is an integer). Since the number of horizontal scanning periods of the output video signal is adjusted so that the non-video signal is periodically inserted, the luminance unevenness does not occur even when the liquid crystal panel 107 is AC-driven.

Further, in the first embodiment, the frequency conversion is performed in the effective video period as usual, and the number of horizontal scan periods constituting one frame period is increased by (L + 1) x by increasing or decreasing the number of horizontal scan periods in the vertical blanking period. The adjustment is made so that it is (2N + 1). By the way, it is conceivable to adjust the number of horizontal scanning periods in the effective video period, but in this case, the image for the line memory 202 as shown in FIG. 29 is increased by increasing the number of horizontal scanning periods in the effective video period. There is a possibility that the timing of signal writing and reading is shifted, and proper transmission of the image signal is impossible only with the line memory 202 for one line. However, in the case of increasing or decreasing the number of horizontal scanning periods in the vertical blanking period as in the present embodiment, since the timing of the image signal writing and reading to the line memory 202 in the effective video period is not affected, the line memory is changed. Without further addition, the number of horizontal scanning periods can be freely increased or decreased. However, in the vertical blanking period, as shown in FIG. 7, non-image signals are recorded in the pixels of the liquid crystal panel 107, so it is not desirable to increase or decrease the number of horizontal scanning periods more than necessary in the vertical blanking period. . This is because the balance of the recording time of the non-image signal collapses, which causes the occurrence of luminance unevenness. Therefore, as long as the number of horizontal scanning periods constituting one frame period satisfies the constraint of (L + 1) x (2N + 1) (N is an integer), the increase or decrease of the number of horizontal scanning periods in the vertical blanking period It is desirable to suppress the width as much as possible. Further, the third embodiment described later is to prevent the collapse of the balance of the recording time of the non-image signal caused by adjusting the number of such horizontal scanning periods.

In addition, the first embodiment has been described assuming that the number of horizontal scanning periods constituting one frame in the input video signal is predetermined. However, since the number of horizontal scanning periods constituting one frame is individually determined according to the format of the video signal (for example, 750P, 1125i, NTSC, etc.), the configuration shown in FIG. 1 can correspond to a plurality of formats. none. To cope with a plurality of formats, for example, a combination of the divided clock number A and the divided clock number B is stored in a table for each video signal format, and the combination of the divided clock number A and the divided clock number B that matches the format of the input video signal is stored. May be read from the table and supplied to the selector 104.

(2nd embodiment)

However, there are cases where the number of horizontal scanning periods constituting one frame in the input video signal varies dynamically. According to the investigation by the inventors of the present invention, for example, when the projection signal of the analog VTR is reproduced at high speed, it has been found that the number of horizontal scanning periods constituting one frame varies dynamically with the reproduction speed. In particular, during the transition period from the normal playback to the high speed playback, or conversely, during the transition period from the high speed playback to the normal playback, the playback speed varies greatly every frame. Hereinafter, as a 2nd Embodiment, the liquid crystal display device which can respond also to such a case is demonstrated.

9 shows the configuration of a liquid crystal display device according to a second embodiment of the present invention. In FIG. 9, the liquid crystal display includes a frequency converter 101, a drive pulse generator 102, a selector 104, a source driver 105, a gate driver 106, a liquid crystal panel 107, and a period discriminator 901. ) And an Hr calculating portion 902. In addition, in FIG. 9, the structure equivalent to FIG. 1 is attached | subjected with the same code | symbol, and description is abbreviate | omitted.

In the present embodiment, even when the number of horizontal scanning periods constituting one frame of a video signal, such as an analog VTR, varies dynamically, the period from the time when the vertical synchronization pulse is input until the effective video period starts is horizontal. The number of syringes is adjusted individually in real time every 1 frame period. First, with reference to FIG. 10, the process of this embodiment is conceptually demonstrated.

In order to adjust in real time the number of horizontal scanning periods of a video signal in which the number of horizontal scanning periods constituting one frame is dynamically changed, in this embodiment, as shown in FIG. 10, vertical synchronization is performed from the start of the effective video period. The number of horizontal scanning periods existing in the period up to the time point at which the pulse is input is counted. Then, the period (adjustment in the drawing) from the time when the count is completed until the effective video period starts so that the number of horizontal scanning periods constituting one frame period in the output video signal becomes an odd multiple of (L + 1) according to the number. Adjust the number of horizontal scan periods included in the period. In addition, since the time from the time point at which the vertical synchronization pulse is input to the start time of the effective video period is constant for each video signal format, it is possible to accurately predict the time point. The above processing can also be applied to a video signal in which the number of horizontal scanning periods constituting one frame is dynamically changed by repeating every frame.

Fig. 11 shows the relationship between the horizontal scanning period before and after frequency conversion in the case where frequency conversion of 1.25 times is performed and one non-image signal is inserted for every four image signals to generate an output video signal. In this embodiment, in order to realize such a process, the frequency division part 101 supplies different frequency division clock numbers in an adjustment period and other period. In particular, the number of divided clocks corresponding to the adjustment period is calculated in real time based on the count result of the number of horizontal scanning periods described above. This process is executed by the period discriminating unit 901, the Hr calculating unit, and the selector 104 shown in FIG. Hereinafter, these operations will be described.

The period discrimination unit 901 determines whether or not the signal currently input to the frequency converter 101 corresponds to the adjustment period based on the input synchronization signal, and outputs the determination result to the selector 104. Specifically, the period from when the vertical synchronization pulses are input until the effective video period starts is determined as the adjustment period. Further, the period discrimination unit 901 counts the number Ve of horizontal scanning periods in the period from the start of the effective video period to the time when the vertical synchronization pulse is input (that is, from the count start point to the count end point shown in FIG. 10). To the Hr calculation unit 902. In addition, the period discrimination unit 901 acquires the number Bp of horizontal scanning periods included in the period from when the vertical synchronization pulse is input until the effective video period starts, and outputs them to the Hr calculation unit 902. do. In addition, for some video signals such as high-speed playback signals of analog VRT, the number of horizontal scanning periods included in the period from the time of input of vertical synchronization pulses until the effective video period starts by insertion of a pseudo horizontal synchronization pulse or the like. Bp fluctuates dynamically. However, even in this case, since the length (temporal length) of the back porch period is constant, the number of horizontal scanning periods can be appropriately adjusted by appropriately using a predetermined setting value during normal reproduction as the value of Bp. It will be apparent from the description below. In addition, the period discrimination unit 901 outputs the horizontal dot clock number of the input video signal to the selector 104 and the Hr calculation unit 902 as the divided clock number Ht. The function of the period discrimination unit 901 as described above can be realized by, for example, a video signal processing processor.

The Hr calculating unit 902 calculates the frequency division clock number Hr for the adjustment period based on the values of Ve, Bp, and Hr supplied from the period discriminating unit 901. If the function F (x, n) is defined as a function which returns the value closest to x among the values of the radix multiple of n, Hr is calculated as follows. L is the number of gate lines at which non-image signals are simultaneously written.

As a result, for example, in the example of FIG. 11, Hr = 75. Antacid

Although various configurations can be considered as hardware for realizing the function F, the function F (x, 4) can be expressed as follows in the case of n = 4 (that is, in the case of L = 4). However, int (x) is a function that returns an integer that does not exceed x.

In this case, since int (x / 8) x 8 can be easily realized by lower 3 bit cutting, the Hr calculation unit 902 can be realized with a very simple configuration as shown in FIG. In addition, since there are generally various configurations as the divider, an optimal configuration can be selected in consideration of the operation speed and the circuit size. In this embodiment, since the calculation must be completed at least shorter than the adjustment period (preferably, shorter than the horizontal scanning period), the subtractive configuration is inappropriate because the calculation is late, and the Newton-Raphson method (Newton-Raphson) method), a calculation method, a table lookup, and the like are preferable.

The selector 104 selects the divided clock number Hr output from the Hr calculator 902 in the adjustment period based on the determination result of the period discrimination unit and supplies it to the frequency converter 101 in the period other than the adjustment period. The number of divided clocks Ht output from the period discrimination unit 901 is selected and supplied to the frequency converter 101. The frequency converter 101 generates an output video signal based on the number of divided clocks supplied from the selector 104.

As described above, according to the second embodiment, since the number of horizontal scanning periods of the input video signal can be adjusted in real time, even in the case of handling a video signal in which the number of horizontal scanning periods constituting one frame is dynamically changed, the first embodiment Similarly, luminance nonuniformity does not occur.

In addition, in the second embodiment, the adjustment period is defined from the time point at which the vertical synchronization pulse is input to the start point of the effective video period, but the present invention is not limited thereto, and for example, only the back porch may be the adjustment period. However, as the adjustment period becomes shorter, the degree of freedom of adjustment decreases. Therefore, the adjustment period is preferably as long as possible.

(Third embodiment)

As described above in the description of the first embodiment, no image signal is recorded in the vertical blanking period, but as shown in Fig. 7, non-image signals are recorded in the pixels of the liquid crystal panel 107, so that horizontal scanning is performed in the vertical blanking period. If the number of periods is increased or decreased more than necessary, the balance of the recording time of the non-image signal is broken, which causes the occurrence of luminance nonuniformity. For example, in the example of Fig. 7, increasing the number of horizontal scanning periods in the vertical blanking periods shortens the length of one horizontal scanning period relatively, and reduces the recording time of the non-image signal. As a result, it is impossible to sufficiently record the non-image signal, and as a result, the region in which the non-image signal is recorded in the vertical blanking period (the region on the gate line corresponding to the gate pulses P1 to P12 in the example of FIG. 7) is effective. In the region where the non-image signal is recorded in the video period (the region on the gate line corresponding to the gate pulses P13 to P40), a luminance difference occurs. In addition, since the boundary between these areas always appears in the same place, even a slight luminance difference is likely to be perceived. In the third embodiment, for the horizontal scanning period in which the non-image signal is recorded in the vertical blanking period, the length is controlled to be equal to the length of the horizontal scanning period in the effective video period to prevent variations in the recording time of the non-image signal. It features.

13, the outline | summary of the operation | movement of the liquid crystal display device which concerns on 3rd Embodiment is demonstrated. In FIG. 13, the input video signal is the same as that shown in FIG. 6, and the frequency conversion of 1.25 times is also the same as the example shown in FIG. 13 and 6 differ in the length of the horizontal scanning period in the vertical blanking period of the output video signal. Specifically, in the example of FIG. 13, the length of the horizontal scanning period in the effective image period (here 320) for the horizontal scanning period corresponding to the timing at which the non-image signal is actually recorded in the pixel on the liquid crystal panel 107 in the vertical blanking period. The length of the horizontal scanning period which is the same length as iii) and which corresponds to the timing at which the non-image signal is actually recorded in the pixel on the liquid crystal panel 107 for the other horizontal scanning periods is longer than that of the example (265.6 ms) shown in FIG. It is shorter than the example shown in Fig. 6 in consideration of the elongation (252.8 kV). The horizontal scanning periods corresponding to the timing at which the non-image signal is actually written to the pixels of the liquid crystal panel 107 are three horizontal scanning periods among 15 horizontal scanning periods included in the vertical blanking period, as shown in FIG. In the first horizontal scanning period of the three, non-image signals are simultaneously written to the pixels on the gate line corresponding to the gate pulses P1 to P4, and at the second horizontal scanning time, the non-image signals are gate pulses P5 to P8. Are simultaneously written to the pixels on the gate line corresponding to the non-image signal at the same time to the pixels on the gate lines corresponding to the gate pulses P9 to P12 during the third horizontal scanning period.

In order to realize the above operation, the number of divided clocks in the horizontal scanning period corresponding to the timing at which the non-image signal is actually recorded in the pixel on the liquid crystal panel 107 in the vertical blanking period is 83 (the output video signal shown in Fig. 6). And the number of divided clocks of other horizontal scanning periods in the vertical blanking period corresponding to the increase, while increasing the number of divided clocks in the horizontal scanning period of the vertical blanking period in It is good to reduce evenly by 4 (rounding off after a decimal point) and to make 83-4 = 79. The specific structural example of 3rd Embodiment is shown in FIG. In FIG. 14, the period discrimination unit 1401 outputs "1" during the vertical blanking period except for the horizontal scanning period corresponding to the timing at which the non-image signal is actually written to the pixel on the liquid crystal panel 107. "0" is output for the other period. In the above example, 100 may be set as the divided clock number A to be supplied to the selector 104 and 79 as the divided clock number B in advance.

Further, in the above example, it is assumed that the number of horizontal scanning periods constituting one frame period of the input video signal is the same as in the first embodiment, but horizontally constituting one frame period of the input video signal as in the second embodiment. The third embodiment can also be applied when the number of syringes fluctuates dynamically. The structure in that case is shown in FIG. In Fig. 15, the period discrimination unit 1501 outputs " 1 " for the period except for the horizontal scanning period corresponding to the timing at which the non-image signal is actually written to the pixel on the liquid crystal panel 107 during the adjustment period, and other periods. Outputs "0" for. The Hr calculating part 1502 calculates Hr as follows. Further, the function F (x, n) is a function of returning the value closest to x among the radix multiples of n, and L is the number of gate lines at which non-image signals are simultaneously written.

In the above formula, Hro corresponds to Hr in the second embodiment. In the case where the input video signal is the same as that shown in Fig. 10 and frequency conversion is performed at 1.25 times (that is, in the case of L = 4), Hr becomes 68 (decimal point or less).

The selector 104 selects Ht or Hr based on the discrimination result of the period discrimination unit 1501 and outputs the Ht or Hr to the frequency converter 101, and the frequency converter 101 supplies the number of divided blocks supplied from the selector 104. On the basis of this, an output video signal as shown in Fig. 16 is output.

In the above description, the horizontal scanning period corresponding to the timing at which the non-image signal is actually recorded in the pixel on the liquid crystal panel 107 in the vertical blanking period is unconditionally equal to the length of the horizontal scanning period in the invalid image period. When only considering that the lack of recording of the non-image signal in this period is prevented, Ht may be used as the divided clock number in this period only when Hro < Ht. For example, in the case (Hro = 110, Ht = 100) as shown in FIG. 8, since there is sufficient recording time of the non-image signal in the vertical blanking period, the horizontal scanning period corresponding to the timing at which the non-image signal is recorded. Hro 110 may be used as is as the divided clock number.

As described above, according to the third embodiment, for the horizontal scanning period in which the non-image signal is recorded in the vertical blanking period, the length of the non-picture signal is varied by controlling the length to be equal to the length of the horizontal scanning period in the effective video period. Can be prevented and luminance unevenness can be prevented.

(4th Embodiment)

By the way, in the above-mentioned first embodiment, the length of each horizontal scanning period included in the vertical blanking period in the output video signal is equal, but as a result of increasing or decreasing the number of horizontal scanning periods included in the vertical blanking period, The length of the horizontal scan period and the length of the horizontal scan period in the vertical blanking period may vary greatly. The larger this difference is, the more uneven luminance occurs on the screen. The larger this difference is, the more uneven luminance occurs on the screen. The principle will be described with reference to FIGS. 17 and 18.

In the reverse transition prevention driving, image signals and non-image signals are recorded alternately once in one frame period. In Fig. 17, an image signal holding period (a period from the time an image signal is recorded to the next non-image signal is recorded) and a non-image signal holding period (the non-image signal is recorded next) after each line are recorded. Period of time until Fig. 18 shows the ratio of the image signal holding period and the non-image signal holding period in one frame period for each line. As shown in Fig. 18, the ratio is changed by lines. This is because the length of the horizontal scanning period is different between the vertical blanking period and the effective image period. The fourth embodiment is characterized by making it difficult to perceive such luminance unevenness.

19 shows the configuration of a liquid crystal display device according to a fourth embodiment of the present invention. In FIG. 19, the liquid crystal display device includes a frequency converter 101, a drive pulse generator 102, a period discriminator 103, a source driver 105, a gate driver 106, and a liquid crystal panel 107. ) And a selector 1901. In addition, in FIG. 19, the same code | symbol is attached | subjected to the structure equivalent to FIG. 1, and description is abbreviate | omitted.

The third embodiment is characterized in that the number of divided clocks is gradually changed in the effective video period and the vertical blanking period instead of the binary method as in the first embodiment. The operation of the third embodiment will be described below by taking an example where the input video signal is a signal as shown in FIG.

The selector 1901 is supplied with 15 divided clock numbers. The divided clock numbers are set to 95, 91, 86, 82, 78, 77, 77, 77, 77, 77, 78, 82, 86, 91, 96, etc., in order, and the selector 1901 is vertical. The frequency converter 101 is supplied to the frequency converter 101 while sequentially switching the divided clock numbers in the blanking period. The sum of the divided clock numbers is determined according to the length of the vertical blanking period. For example, in the above example, since the vertical blanking period is 20 x 10/50 = 4 ms, the number of divided clocks is set so that the sum of the divided clock numbers is 312.5 ms x 4 ms = 1250. 20 shows the relationship between the horizontal scanning period before and after the frequency conversion. 21 shows the relationship of the length of each horizontal scanning period in the vertical blanking period.

As a result of the above control, the ratio of the image signal holding period and the non-image signal holding period in one frame period for each line has a higher luminance non-uniformity state than in the example shown in FIG. It becomes a preferable state.

(5th Embodiment)

In the first to fourth embodiments, the number of horizontal scanning periods is adjusted by controlling the number of horizontal scanning periods by controlling the number of divided clocks supplied to the frequency converter 101. However, the present invention is not limited to this. The same effect can be achieved by switching clocks with the number of divided clocks fixed. Hereinafter, as a fifth embodiment, a configuration for switching the clock supplied to the frequency converter in the effective video period and the vertical blanking period will be described.

Fig. 23 shows a configuration of a liquid crystal display device according to a fifth embodiment of the present invention. In FIG. 23, the liquid crystal display device includes a driving pulse generator 102, a period determination unit 103, a source driver 105, a gate driver 106, a liquid crystal panel 107, a frequency converter 2301, and a selector 2302. ). In addition, in FIG. 23, the same structure as that of FIG. 1 is attached | subjected with the same code | symbol, and description is abbreviate | omitted.

The selector 2302 is supplied with a clock A (312.5 kHz) and a clock B (375 kHz) having different frequencies, and the selector 2302 selects one of the clocks according to the discrimination result of the period discrimination unit 103 and selects a frequency. It supplies to the conversion part 2301. Specifically, clock A is output during the effective video period and clock B is output during the vertical blanking period.

24 shows a configuration of the frequency converter 2301. Incidentally, in Fig. 24, the same components as those in Fig. 2 are denoted by the same reference numerals and the description thereof will be omitted. The control signal generator 2401 uses the clock supplied from the selector 2302 as the read clock of the line memory 202. That is, data is read from the line memory 202 based on a clock of 312.5 ms in the effective video period, and data is read from the line memory 202 based on a clock of 375 ms in the vertical blanking period. As a result, the relationship between the horizontal scanning period before and after the frequency conversion is as shown in FIG. Therefore, the number of horizontal scanning periods constituting one frame period in the output video signal is an odd multiple of (L + 1), and the same effect as in the first embodiment can be obtained.

In the fifth embodiment, the selector 2302 is configured to switch clocks. However, the present invention is not limited to this, and may be configured to appropriately change the frequency of a single clock using, for example, a PLL. .

However, it is known that the blurring of the moving picture peculiar to the hold display element is improved and the moving picture display performance of the liquid crystal panel is improved by applying the black level non-picture signal to the liquid crystal cell for each frame for a predetermined period. The driving for applying the black level non-picture signal to the liquid crystal cell for a predetermined period of time for each frame and the reverse transition prevention driving are only differences between whether the non-picture signal is a black level signal or a high voltage signal. Therefore, even when the black level non-picture signal is applied to the liquid crystal cell for a predetermined period of every frame, the luminance nonuniformity is generated on the same principle as when the reverse transition prevention driving is performed, and the same method as in the above-described embodiments is used. The luminance nonuniformity can be prevented. Therefore, the present invention is not limited to driving the liquid crystal panel of the OCB mode, but can also be applied to driving the liquid crystal panel of other modes (for example, TN mode).

As described above, according to the present invention, for example, when the reverse transition prevention driving is performed using the liquid crystal panel of the OCB mode, the increase of the driving frequency is suppressed, and the luminance unevenness caused by the AC driving of the liquid crystal panel is also prevented. The cost can be reduced.

Claims (18)

A liquid crystal display device which displays an image by driving a liquid crystal panel based on an input image signal. A liquid crystal panel having a plurality of source lines and a plurality of gate lines; Between the image signals constituting the input video signal, a non-image signal simultaneously recorded in pixels on L gate lines of the liquid crystal panel is spaced one line from an image signal of L (L is an integer of 2 or more) lines. The number of horizontal scanning periods of the output video signal such that the number of horizontal scanning periods forming one frame period is (L + 1) × (2N + 1) (N is an integer). A frequency converter for adjusting the A driver for driving the liquid crystal panel based on the output image signal generated by the frequency converter; And the frequency converter adjusts the number of horizontal scanning periods forming one frame period by increasing or decreasing the number of horizontal scanning periods included in the vertical blanking period. The method of claim 1, The liquid crystal panel is an OCB mode liquid crystal panel, wherein the non-image signal is a signal for applying a predetermined high voltage to the liquid crystal of the liquid crystal panel to prevent reverse transition. The method of claim 1, And the non-image signal is a black level signal. The method of claim 1, And the frequency converter generates the output image signal based on different frequency division clocks in an adjustment period included in a vertical blanking period and a period other than the adjustment period in one frame period. The method of claim 4, wherein A period discrimination unit for discriminating whether or not an image signal supplied to said frequency converter corresponds to said adjustment period based on a synchronization signal synchronized with an input video signal; And a selector for supplying different frequency division clocks to the frequency converter in the period other than the adjustment period and the adjustment period of one frame period, based on the determination result of the period discrimination unit. . The method of claim 4, wherein The adjustment period is a period from the input time of the vertical synchronization pulse to the end of the vertical blanking period, A division clock count calculation unit for calculating a division clock number corresponding to the adjustment period subsequent to the period based on the number of horizontal scanning periods included in the period from the start of the effective picture period to the input time of the vertical synchronization pulse; Liquid crystal display characterized in that. The method of claim 1, The frequency converter inputs the vertical synchronization pulses from the start of the effective area period. On the basis of the number of horizontal scanning periods included in the period up to the output time point, the number of horizontal scanning periods included in the period from the time of inputting the vertical synchronization pulses to the end of the vertical blanking period increases or decreases. Display. The method of claim 1, The frequency converter is arranged in a period in which the length of the horizontal scanning period corresponding to the timing at which the non-image signal is written to the pixel of the liquid crystal panel in the adjustment period included in the vertical blanking period is less than the adjustment period in one frame period. And an output image signal which is equal to or greater than the length of the horizontal scanning period. The method of claim 1, And the frequency converter generates an output image signal having substantially equal lengths in each horizontal scanning period in the adjustment period included in the vertical blanking period. The method of claim 1, And the frequency converter generates an output image signal in which the length of each horizontal scanning period is gradually changed in the adjustment period included in the vertical blanking period. A driving method of a liquid crystal display device for displaying an image by driving a liquid crystal panel having a plurality of source lines and a plurality of gate lines based on an input image signal, Between the image signals constituting the input video signal, non-image signals recorded simultaneously on the pixels on the L gate lines of the liquid crystal panel are spaced one line apart from the image signals of the L (L is an integer of 2 or more) lines. To generate an output video signal, and add the horizontal scanning period of the output video signal such that the number of horizontal scanning periods constituting one frame Adjust, Driving the liquid crystal panel based on the output image signal; A method of driving a liquid crystal display device, characterized by adjusting the number of horizontal scanning periods constituting one frame period by increasing or decreasing the number of horizontal scanning periods included in the vertical blanking period. The method of claim 11, And the output image signal is generated on the basis of different divided clock numbers in a period other than the adjustment period included in the vertical blanking period and the adjustment period in one frame period. The method of claim 12, Discriminating whether or not each image signal constituting the input image signal corresponds to the adjustment period based on a synchronization signal synchronized with the input image signal; Based on the determination result, a number of different divided clocks is selected in a period other than the adjustment period and the adjustment period of one frame period; And generating the output image signal based on the selected divided clock number. The method of claim 12, The adjustment period is a period from the input time of the vertical synchronization pulse to the end of the vertical blanking period, The number of divided clocks corresponding to the adjustment period following the period is calculated based on the number of horizontal scanning periods included in the period from the start of the effective image period to the input time of the vertical synchronization pulse. Driving method. The method of claim 11, The horizontal scanning period included in the period from the input point of the vertical synchronization pulse to the end of the vertical blanking period based on the number of horizontal scanning periods included in the period from the start of the effective picture period to the input time of the vertical synchronization pulse. A method of driving a liquid crystal display device, characterized by increasing or decreasing the number of. The method of claim 11, In the adjustment period included in the vertical blanking period, the length of the horizontal scan period corresponding to the timing at which the non-image signal is written to the pixels of the liquid crystal panel is equal to the horizontal scan period in the period other than the adjustment period in one frame period. A drive method for a liquid crystal display device, characterized in that for generating an output video signal of length or more. The method of claim 11, And an output image signal of substantially equal length in each horizontal scanning period in the adjustment period included in the vertical blanking period. The method of claim 11, And an output image signal of which the length of each horizontal scanning period is gradually changed in the adjustment period included in the vertical blanking period.